Brainwave Entrainment refers to the process of directing human brainwave towards a desired frequency. We are able to do thinks thanks to a natural faculty of the brain called the 'Frequency Following Response'. This is the tendency for the frequnecy of the brain to match a dominant frequnecy that is presented to it.
So for example, if you were to stare at repetitive flashing light like a strobe light, your brianwave would begin to synchronise with the frequnecy of the pulses of light.
It is possible to entrian the brain to a certain frequency by visual stimulation as in the example above, or by audio stimulation in which a tone at the desired frequency is used.
Brainwave Entrianment is a powerful tool due to the fact that each specific brainwave frequnecy has associated with it a characteristic metnal state. So by entraining to certain frequnecies you can also entrain to certain states of mind. This has significant applicaiotns for people who have difficulty sleeping, being able to realx, maintaining focus, and staying alert.
Since there also mental states associated with accelerated learning, and peak performance of physical activities, brianwave entrianment can be useful in achieving these states.
For a good introduction to the science, history and uses of brainwave entrainment, see the squidoo page; a Quick Guide to Brainwave Entrainment
